不同品种辣木叶多糖的理化性质和抗氧化活性研究

Physicochemical Characterization and Antioxidant Activity of Polysaccharides from Different Varieties of Moringa oleifera Leaves

摘要:

本文选取三个品种的辣木叶：印度改良种辣木（Periyakulam 1，PKM1）、PKM1改良种辣木（Improved Periyakulam 1，PKM2）、非洲辣木（Moringa stenopetala），采用热水浸提法制备三种活性多糖，对它们的理化性质及抗氧化活性进行比较研究。结果表明PKM1辣木叶的多糖得率最高，为6.84%，其次为PKM2辣木叶和非洲辣木叶；三种辣木叶多糖的总糖、蛋白质、葡萄糖醛酸和半乳糖醛酸含量不同。结构分析表明三种辣木叶多糖的分子量大小分布不同，且均由半乳糖、阿拉伯糖、岩藻糖、木糖组成。红外光谱分析表明三种辣木叶多糖是β构型的酸性呋喃多糖，具有相似的官能团。原子力显微镜和刚果红实验表明PKM1辣木叶多糖呈链状构象，而PKM2和非洲辣木叶多糖呈类球形构象，在弱碱性溶液中形成三螺旋构象。体外抗氧化活性结果表明三种辣木叶多糖均具有良好抗氧化活性，且PKM1和非洲辣木叶多糖的抗氧化活性相当，优于PKM2辣木叶多糖。

Abstract:

In this study, three water-soluble polysaccharides were extracted from three varieties of Moringa oleifera leaves, including Periyakulam 1 (PKM1) leaves, Improved Periyakulam 1 (PKM2) leaves and M. stenopetala leaves. The physicochemical properties and antioxidant activities of these polysaccharides were comparatively investigated. The results showed that PKM1 leaves had the highest polysaccharide yield of 6.84%, followed by PKM2 leaves and M. stenopetala leaves. Three polysaccharides had different content of carbohydrate, protein, glucuronic acid and galacturonic acid. Structural analyses showed that three polysaccharides had different molecular weight distributions, and consisted of galactose, arabinose, fucose, and xylose. Fourier transform-infrared (FT-IR) spectra indicated that three polysaccharides were acidic furanose polysaccharides with β-configuration and have similar functional groups. Atomic force microscopy (AFM) and congo red analyses showed that PKM1 polysaccharide exhibited chain conformation, while PKM2 and M. stenopetala polysaccharides exhibited spherical conformation. In addition, they could form helical conformation in weak alkaline solution. In vitro antioxidant activity assay indicated that three polysaccharides had favorable antioxidant activities, and the polysaccharides from PKM1 and M. stenopetala leaves were higher than PKM2.